Collagen, one of the most abundant proteins of the extracellular matrix, provides structural integrity in the human body and is responsible for multiple interactions with cells and other matrix molecules. Many common diseases, such as arthritis, diabetes, and cancer involve abnormal regulation or reactivity of collagen and certain collagen genetic diseases result in connective tissue disease or aortic aneurism. The objective of this proposal is to develop a mechanistic understanding of the interactions of the collagen ligand with its receptors and to understand the molecular basis of Osteogenesis Imperfecta (OI), a genetic disease that results in brittle bones. We propose to use an integrated approach based on NMR in conjunction with computational, biophysical methods, and in vitro functional assays to provide unique structural and dynamic insight these questions. The specific aims of the proposal include 1) characterizing the structure and dynamics of the interactions between the integrin I domain and collagen; 2) defining the sequence dependence and molecular mechanism of Gly mutations leading to collagen diseases: prediction of OI phenotype and 3) characterizing interactions of matrix metalloproteinases (MMPs) and integrin I-domain receptors with triple helical motifs that contain imperfect (GXY)n sequences at, or near, the binding regions. In order to achieve these aims we will develop some novel methodology designed to 1) achieve better structural and dynamic characterization of the collagen model peptides; these are long anisotropic molecules that are difficult to characterize by standard protocols and integration of NMR and MD simulations will provide a new approach for investigation of these unusual systems. 2) Using statistical approaches, develop consensus sequence patterns that define lethal and nonlethal phenotypes in OI; these will be used to begin to establish predictions of phenotype based on sequence and conformational fluctuations. The biomedical importance of collagen has led to increasing interest in the structural and biological role of this protein makin the collagen triple helix an extremely important target for probing sequence-structure-function relationships and for understanding the molecular basis of collagen/receptor biological interactions. Characterizing the collagen triple helix conformation and dynamics alone, and in combination with its binding partners, will help understand its role in disease and ligand recognition, and aid in drug discovery programs.